This invention pertains to a flexible storage tank which is made of collapsible flexible material for the storage of liquid or particulate flowable material. It has separate inner and outer tanks, the inner tank or bladder being made of a flexible pliant material which may be individually selected to be impervious and non-reacting to the contents and an outer tank which is made of much stronger material and which acts as a restraint to maintain the inner tank in a desired generally truncated conical shape.
Hereinafter for convenience the inner tank will be referred to as a "liner" and the outer tank will be referred to as a "restraint".
Currently all known collapsible fabric tanks on the market are manufactured from coated fabrics. These fabrics serve as both the restraint means and the fluid retention means. This design works very well for holding fuel or water; however, when used for other chemicals a number of problems arise. First if the chemical is a viscous material such as latex, cleaning of the tank is extremely difficult if not impossible. This means that the tank can only be used for that specific material, and even then the inside surface quickly becomes coated with hardened product which may flake off into the fresh latex. Secondly, the coated materials limit the chemical resistance which can be obtained by such a tank (i.e. most tanks utilize either urethane coated fabrics, or nitrile type rubber coated fabrics). The ability to use films such as Teflon, polyethylene, etc. greatly enhances the ability of the tank to withstand a wide spectrum of chemicals.
In addition, typical collapsible fabric tanks have a small aspect ratio (i.e. they tend to have a large footprint as compared to their height). This may be objectionable if it is being applied in an area which imposes floor space restrictions.